Chapter 9 - "The Writing on the Wall" - In which HRH are questioned about the Petrified cat, Hermione asks Professor Binns about the Chamber of Secrets, HRH return to the scene of the crime, consult Moaning Myrtle, and speculate about the mystery.

The Deathday Party and What Came After
On the way to the Great Hall, Harry hears the voice in the walls again and chases it - stopping dead when he finds Mrs. Norris strung up by her tail and a message written in blood. He, Hermione, and Ron stand frozen, and soon the rest of the school arrives - led by a gloating Draco Malfoy.
The Basilisk's First Attack
At the scene of the attack on Mrs. Norris, Filch arrives, screaming, and immediately accuses Harry of committing the crime. [Dumbledore] soon rushes in, though, and whisks Filch and the [petrified] Mrs. Norris, along with Harry, Ron, and Hermione, to Lockhart's office.
With teachers gathered around the [Petrified] Mrs. Norris, Lockhart rambles endlessly about himself, [Dumbledore] determines that Harry wasn't involved, Filch fumes that Harry saw his Kwikspell letter, and Snape tries unsuccessfully to get Harry kicked off the [Quidditch team]. Snape also agrees to make [Mandrake Restorative Draught], rather than let Lockhart do it.
Harry, Ron, and Hermione, dismissed from Lockhart's office, run back toward Gryffindor Tower. On the way they discuss the voice Harry's been hearing, and the newfound knowledge that Filch is a [Squib].
As time passes Filch tries unsuccessfully to clean the corridor where Mrs. Norris was [Petrified], Ginny seems greatly disturbed by Mrs. Norris's fate while Ron tries to reassure her, and Hermione spends every spare moment she has in the library.
Suspicions and Worries
Harry runs into Justin Finch-Fletchley in the hallway, and before he can say hello Justin promptly turns around and rushes the other direction.
Harry finds Ron and Hermione in the library and tells them about Justin's avoiding him. Meanwhile Hermione tells them that she's been trying, unsuccessfully, to read up on the Chamber of Secrets.
A boring History of Magic class is interrupted when Hermione asks Professor Binns to tell the class about the Chamber of Secrets. After some convincing, he explains the story of Salazar Slytherin fighting with Godric Gryffindor and creating the mythical chamber beneath the school.
Leaving History of Magic, Ron and Hermione talk about the Chamber of Secrets and the evils of Slytherin while Harry silently thinks about how the Sorting Hat almost made him a Slytherin. He also realizes, thanks to Colin Creevey, that people now think he's the [heir of Slytherin].